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BS IV Norms

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  • To the dismay of many automobile manufacturers sitting on a huge inventory of BS III compliant vehicles, the Supreme Court recently ordered that only vehicles with engines compliant with BS IV standards must be sold from April 1, 2017.
  • Authorities have also been prohibited from registering vehicles that don’t meet BS IV norms henceforth, except on proof that the vehicle was sold on or before March 31.

What are BS norms?

  • Introduced in 2000, the Bharat norms are emission control standards that are based on the European regulations (Euro norms).
  • They set limits for release of air pollutants from equipment using internal combustion engines, including vehicles. Typically, the higher the stage, the more stringent the norms.
  • Major emissions governed under these norms are carbon monoxide emissions, hydrocarbon emission limits. Nitrogen Oxides and particulate matter are also significant metrics. Furthermore, for every step up in standards, an improved standard of fuel is required.
  • The BS IV norms were introduced in 13 cities apart from the National Capital Region from April 2010 onwards.
  • According to the roadmap, the entire nation was to be covered under BS IV by April 1, 2017.
  • BS IV fuel was also to be made available across the country from April 1 this year.
  • BS IV norms stipulate only 50 parts per million sulphur compared with up to 350 parts per million under BS III. Also, hydrocarbon, nitrogen oxide and particulate matter emissions are lower under BS IV.

What are the technologies used for BS IV?

For two vheelers –

  • Changes from BS3 to BS4 for motorcycles are more than just tailpipe emissions. Regulations also (for the first time) restrict evaporation emissions from fuel tanks, which mean a new breather value and additional or changed stamps in the body structure or additional brackets that hold these new systems. This is very difficult to retrofit considering the fact that major design changes might be needed.
  • Coming to tail pipe emissions, BS4 motorcycles in most cases require larger catalytic converters in terms of flow volumes to eliminate harmful nitrogen based gasses. And although that could be adapted within the exhaust system, most bikes also need a secondary airflow system that adds oxygen (or natural air) to the exhaust stream just before the catalytic convertors. This of course, is a more complex system for which retro fitment is more difficult.
  • Many manufacturers have also resorted to a more complex ECU and ignition control setup that has more than the standard idle map and full throttle map for a better control of the ignition timing which in turn makes for a cleaner burn and thus, less pollution. The byproduct of this is also a more linear acceleration curve and better fuel economy.

For Petrol Powered Passenger vehicles  and SUVs

  • Most petrol powered passenger cars in India have already converted to BS4 years ago. This is mainly because the change from BS3 to BS4 is easiest for internal combustion petrol engines.
  • Most emissions standards are met by the engines themselves without the need for complex post combustion methods to reduce the effect of pollution. The addition of turbocharged smaller capacity engines for example is not for more power or more fun but because it is very easy to attain BS4 emissions levels with these modern engines.
  • Even naturally aspirated internal combustion engines that are slightly older in terms of technology can meet BS4 with a larger catalytic convertor or two catalytic convertors either in pre-engineered form or retrofitted. Ideally, the catalytic convertors in series is the solution to go for, with one mounted right after combustion occurs (normally on the exhaust manifold itself) and one mounted as a part of the pre muffler package or just before the pre muffler package. The secondary catalytic convertor can also be mounted before or as an in built part of the end can. Similar volume catalytic convertors with a higher concentration of Platinum Group Metals (PGM) can also result in lower emissions if packaging is an issue.
  • It is easiest to retrofit petrol powered passenger cars as most of them already have an on board diagnostics or OBD 2 port, which controls engine behavior in real time. The OBD 2 port and real time emissions control is mandatory for BS4.

For Diesel powered passenger vehicles and SUVs

  • They are the small portion of the passenger car segment that will get slightly affected by the BS3 to BS4 move as there were still a few manufacturers like Mahindra and Tata Motors manufacturing BS3 vehicles for rural and semi urban markets. These vehicles will now be rendered defunct and in most cases, these were mere variants of BS4 enabled cars that are already available in the market (for example: Mahindra Thar).
  • The implementation of BS3 had anyways made most manufacturers switch to electrical fuel management and common rail technology for the diesel engines as meeting BS3 with older direct injection technology was quote tough anyways. That said, just like the petrol powered cars, the biggest change in terms of emissions control hardware is a larger volume catalytic convertor or Diesel Oxidation Catalyst (DOC) as it is known specifically for diesel engines. The new BS4 cars will also have to have atleast one NOX sensor in the tail pipe to constantly monitor and a particulate filter to capture particulate matter.
  • On board diagnostics or OBD 2 ports in passenger diesel powered vehicles will be mandatory to ensure real time engine performance adjustments based on pollutant levels. These are very difficult to incorporate into older technology.
  • While passenger cars and two wheelers can still take some form of retro fitment, it is the commercial vehicle segment that will go through one of the most revolutionary changes in technology and mechanical advancements in recent history with the new BS4 norms.
  • Retro fitment of emissions control units to meet BS4 is almost impossible or very very difficult as most sytems used are still mechanical and not electronically controlled.
  • The use of on board diagnostics or OBD has been made compulsory not only for passenger cars but also for commercial vehicles which means that all commercial vehicle manufacturers will have to adopt newer ECU based technologies
  • The other addition without which commercial vehicles will not be able to meet emissions is the use of an exhaust gas recirculator or EGR. While mechanical EGR’s with upto 60 percent recirculation has been used in the past for various vehicles in both commercial or passenger segments, the newer BS4 regulations will need electronically controlled EGR units with on the fly adjustment capabilities.
  • In terms of actual hardware post the engine that helps reduce the effect of pollutants, BS3 vehicles today in India do not have any sort of catalyst based system to reduce pollution and have only a noise control muffler that helps reduce audible emissions.
  • The newer trucks and busses, etc will have a mandatory catalytic convertor or Diesel Oxidation Catalyst (DOC) as in the passenger vehicle segment. The DOC will take care of NOX emissions while particulate matter (which includes visible black soot) will be contained with the help of the particulate filers.
  • Certain higher end trucks and busses will also use another type of post engine exhaust which is more advanced. These include a collection of Diesel Oxidation Catalyst (DOC), Lean Nox Catalyst (LNC) and Lean Nox Trap (LNT) and also a Urea injector called the Selective Catalytic Reduction (SCR) module. That said, this technology although used very commonly in Europe is still at a very fledgling stage in India as it needs an occasional top-up of Urea along with regular fuel top ups in order to reduce polluting gasses.
  • To sum up, petrol powered passenger cars will be fastest to adapt followed by two wheelers and diesel passenger cars. Commercial vehicles will have to go though a more engineered approach to meet the BS4 regulations.
  • That said, most vehicles will not just be ‘retrofitted’ with these technologies that we explained earlier to meet BS4 and a more holistic approach to the problem of old unsold stocks will have to be explored.


Why important?

  • While some automakers were betting on April 1, 2017 to be the deadline for the commencement of production of BS IV compliant vehicles and not the sale of such vehicles, the Supreme Court ruling has come not a day too soon.
  • India is on the radar of global automakers as vehicle penetration is still low here, compared to developed countries.
  • Besides, many Indian cities are already among those with the poorest air quality in the world. Upgrading to stricter fuel standards helps tackle air pollution.
  • Other developing countries such as China have already upgraded to the equivalent of Euro V emission norms a while ago.
  • So, India is lagging behind even after implementation of BS IV norms.
  • To compensate for this, BS V standards will be skipped and BS VI norms are proposed to come in by April 2020.
  • Both vehicle manufacturers and fuel suppliers are already working to abide by this deadline.
  • In 2014, the National Green Tribunal said that clean air is a fundamental right.
  • Upgraded emission norms could also mean higher fuel efficiency. BS IV fuel is also being made available pan India, which implies that even your older vehicles can tank up with better fuel.
  • Besides, the Government has been thinking about a ‘cash-for-clunkers’ scheme. If implemented, this will help owners of older and more polluting vehicles to upgrade to BS IV compliant vehicles, with a subsidy from the government.
  • On the flip side, the use of new technology means higher costs for auto makers. This could be passed on to buyers. Oil refiners too have had big capital outlays to produce superior quality fuel under BS IV. So, fuel bills could rise too.



  • Automobile manufacturers’ insistence that huge injustice has been done to them because they have been asked to move to Bharat Stage IV (BS-IV) technologies for emission control before the due date.
  • Thegovernment notification they are using in their defence says companies would stop making Bharat Stage III (BS-III) vehicles by March 31, 2017. The companies say this does not mean that registration of BS-III vehicles would be stopped as of April 1, 2017.
  • Automobile companies, ably represented by their association Society of Indian Automobile Manufacturers, say as a result of the decision to stop registration huge inventories have piled up. This means huge losses for them and for the country. This is injustice, they say.
  • Firstly, vehicles contribute to the pollution that is making us ill.
  • Secondly, improving the quality of fuel and vehicle technology is a critical way to clean up emissions.
  • But thirdly, this improvement in fuel quality and technology has always been hard-fought. It has always come in spite of Indian automobile companies and not because of them.
  • It was inApril 1999 that the Supreme Court had directed that all vehicles in India would have to meet Euro I (BS norms were not fashioned then) by the June of that year. It also directed that Euro II would be mandatory in the NCR by April 1, 2000. At that time, the court had set a precedent by directing that “no vehicle shall be registered unless it conforms to Euro II norms”.
  • In May 1999, counsels for automobile companies argued for more time to implement the Euro norms. The court remarked in obvious sarcasm, “People can’t breathe and you are asking for more breathing time!” The transition happened in Delhi and NCR. Leading companies pushed for technology improvement and the laggards caught up.
  • Thegovernment set up a committee under R A Mashelkar  to finalise the road map for clean fuel technology for the country.
  • In 2003, it was agreed that Delhi, NCR and 12 other polluted cities would get BS-III by April 2005, and the rest of the country by April 2010. Then there was a pause.
  • The 2008 notification only said that Delhi, NCR and 12 other cities would get BS-IV by 2010.
  • In 2015, the road map for the rest of the country was decided—fuel would be progressively made available and technology transition would happen. The deadline was April 1, 2017, when the entire country (barring small remote pockets) would switch to 50-ppm-sulphur fuel as compared to the 350 ppm fuel available till then.
  • The automobile companies, therefore, knew well in advance that the fuel would be available across India by April 1, 2017. The transition to BS-IV is also not new as technologies have been available since 2010.
  • The date of “manufacture” is, then, only a technical argument. The only constraint, that of clean fuel being available nationwide for long-distance carriers like taxis and trucks, has been removed.
  • The case of two-wheelers is slightly different. These are largely petrol vehicles, so fuel is not such a constraint—diesel has high particulate matter and emission control requires stringent quality control in fuel. Thevehicle manufacturers were given an entire year, April 2016 to March 2017, to switch over to BS-IV. Again, the companies knew and the transition should have been seamless.
  • EPCA had convened a meeting in October 2016 to discuss this switch date. The position was that since clean fuel would be available by April 1, 2017, at a considerable cost to the public exchequer, companies should plan their inventories accordingly.
  • The objective was to ask them to reduce the production of BS-III and to ramp up the manufacturing of BS-IV. Instead, the data supplied by the companies to the Supreme Court shows that most of them continued to produce BS-III vehicles at the same or even increased rate. This then built up inventories.
  • The fifth issue is that this transition matters. BS-IV vehicles, particularly diesel trucks, are much less polluting than BS-III. There is 80 per cent reduction in particulate emissions between the two generations. That’s why bringing cleaner vehicles into the market as fast as possible matters.
  • No doubt the country has a massive problem of older and more polluting vehicles. But why should this be an argument for delaying the transition? After all, vehicles have a life of 10-15 years. The faster the new stock takes over the better it is.


Way forward

  • The Supreme Court put it best, “The health of the people is far, far more important than the commercial interests of the manufacturers”.


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